Maintenance of Cetol Teak Finish
Cetol is an awesome product but does require some maintenance. On a yearly basis, a light sanding is necessary with the application of a coat or two to keep up the film. It sounds like there has been no maintenance done for years. You'll have to take the darkened wood down to bare wood, clen it with something like Nu-Teak if you don't like the color after sanding and then build up three coats of the product. After this, annual maintenance is all that should be required. If the surface is gouged, you should apply a coat or two to seal the gouge so the wood doesn't darken.